The Kairuku, or penguins in Ark Survival Evolved are the best way to get organic polymer in the game. Luckily Kairuku are very plentiful on the Island map. Organic polymer is much easier to harvest than it is to make regular polymer, but only stacks to 20 and also spoils.
All the Kairuku are found in the Northwest corner of the Island map, in the arctic biome, which seems like a logical place to find penguins. You will find the most penguins and the safest place to harvest the organic polymer on the iceberg island offshore. The shoreline can be easily accessed on foot, if you can deal with the many nasty creatures there. If you have a flier with good weight, it is much better to get some organic poly there and maybe some oil too, which is plentiful.
Kairuku Island Map Location
29.1 12.7 (SW start)
22.3 09.7 iceberg
16.4 10.1 iceberg
22.0 14.6 shore
16.6 36.9 (NW end)
Hesperornis also yield organic polymer, and can be found almost anywhere on the Island map there is water, but here are two of my favorite locations.